Aetna CEO: Obamacare In A 'Death Spiral' Heading Into 2018. Aetna and Humana have called off their deal amid government concerns over competition. Here's a look back at six pivotal moments that led to this. Aetna and Humana have called off their deal amid government concerns over competition.
For the plant genus, see Synapsis (plant). Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis.
All chemical synapses exhibit the same general sequence of events during the transmission of information across the synaptic cleft. This sequence is always initiated by an action potential that travels down the presynaptic cell (the sending neuron) to its synaptic terminal(s).rag the labels onto the flowchart to indicate the sequence of events that occurs in the presynaptic cell (orange background) and the postsynaptic cell (blue background) after an action potential reaches a chemical synapse.